Muddy waters


Courtesy of SAS Environmental Services Ltd.

Mark Zwinderman of Surface Active Solutions, looks at the dangers involved in the cleaning and maintenance of mud tanks and associated equipment

The oil industry involves many thousands of people working daily in potentially hazardous circumstances with dangerous chemicals and sophisticated engineering equipment. There has been a consistent and determined drive by the industry to reduce the number of health, safety and environmental incidents. The implementation of best practices and improved training has had a measurable impact on the working environment within the oil and gas industry.

These efforts do not take anything away from the fact that many operations carry a very real risk. Wherever people work there will always be the scope for mistakes, communication problems or accidents through equipment failure. One of the best ways to reduce risk is to remove the person from the equation where possible, or at least move the workplace to outside the immediate high-risk areas. Improvements in work place safety can only ever be good for the industry and those involved in hazardous operations.

The correct philosophy is one of approaching the entire process and then assessing where the key areas of risk are, but to remember that these risks are very different in nature. For example, there are health and safety risks, operational risks and environmental hazards.

The cleaning out of supply vessel mud tanks can be a labour intensive and time consuming affair. The traditional method of manual mud tank cleaning involves teams of trained personnel entering contaminated mud tanks, often erecting scaffolding in order to gain access to the higher parts of the wall and the roof of the tank.

This approach is required because of the nature of most drilling mud. It is difficult to remove, and often significant layers of settled solids contaminated with base oil are found at the base of the storage tanks. These settled solids have to be manually removed by teams of personnel working in what is a challenging environment, a confined space filled with hydrocarbons and a range of other chemicals.

Manual cleaning and waste removal approach carries. with it a number of risks. There is a substantial requirement for man entry in the tank in order to set up the scaffolding and for the subsequent cleaning. Also, the use of ultra high-pressure water jetting systems further adds to the potential issues that need to be carefully addressed in carrying out these operations.

This approach subsequently results in large volumes of slop waste, which is heavily contaminated with drilling fluid. And, in the process of cleaning the mud pits on the rigs and the cleaning of the mud tanks in platform supply vessels and barges, there is the added complication of tightened environmental legislation in Europe, putting pressure on the logistics and costs of operations. The cost of disposing of hazardous waste in landfill sites is increasingly expensive as the number of available sites is reduced by European legislation coming into effect.

These factors work together to create a situation where there is space for a new way to approach an old issue, namely the development of micro-emulsion delivery systems for the cleaning of drilling rig mud pits and platform supply vessels, and when paired with an innovative mechanical delivery system, microemulsion chemistry technology really reaches a new optimised level of tank cleaning with fewer health and safety issues compared to the traditional method of operation.

In order for the new system to radically improve the HS&E profile of the operations a number of components need to be altered. These components are the delivery system of the cleaning product, the cleaning product itself and the subsequent handling of the created waste materials.

The micro-emulsion delivery system is an automated tank cleaning system or so-called cleaning in place system (CIP). These consist of designed skids containing filtration and pumping equipment capable of delivering sufficient pressure and flow to deliver a micro-emulsion solution to as many as four mud tanks at a time.

Through the use of geared cleaning nozzles, the entire inside of a mud tank can be covered with a microemulsion cleaning solution within a matter of minutes. These nozzles are placed within the tank using tripods or magnetic fixings and can be moved around at will.

Man entry into mud tanks is minimised to the setup required, a fraction of the time required using the manual cleaning method. Only two men need to enter a tank at any time and only in order to place the cleaning nozzles and hook up the required hoses.

Once the cleaning nozzles are in place and connected to the CIP system, the micro-emulsion cleaning solution is pumped through the system and breaks up the drilling mud on the tank walls and the mud cake on the tank floor. The resulting low viscous liquid waste can be easily removed using standard pumping equipment.

By applying a highly effective and environmentally sound micro-emulsion based cleaning chemical to the water used there is no need for ultra high pressure jetting equipment. In addition the complete destruction of the integrity of the mud cake within the tank, including the breakdown of the solids at the base of the tank, allows for a very fast cleaning cycle.

The resulting slurry of water, micro-emulsion chemical and removed mud is easily pumped from the tank and can be treated in a straightforward manner. The chemical is recycled with the wash water and the oil and solids are separated using gravity settling or decanter centrifuges.

Although similar systems have been installed in some cases they are rarely used to great effect as the cleaning nozzles have limited resistance to solids loading in the return washing fluid. With the use of micro-emulsion chemistry these solids are now easily removed from the returns, leaving a solid free recycled washing fluid.

This allows for a continuous mud tank cleaning process either onshore for the processing of supply vessels or offshore on the rig. These CIP systems are very compact and easily installed as either fixed components of the rig mud pit system or can be designed to be portable. Because of the modular design it is possible for each company implementing the system to specify the solids separation equipment used or indeed use that equipment already available.

The use of these CIP systems combined with micro-emulsion chemistry therefore results in greatly reduced man entry requirements into a hazardous workplace. In addition the environmental risks are reduced through waste reduction and by generating waste that allows for straightforward handling and treatment.

Surface Active Solutions

Mark Zwinderman is operations director at Surface Active Solutions (SAS), a single source for the provision of specialist products and services to solve environmental issues for the global oil and gas industry.

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